Enable MockHttpTransport in ShardChangsIT

CCR side of #29601

Author: dnhatn

x-pack/plugin/ccr/src/test/java/org/elasticsearch/xpack/ccr/ShardChangesIT.java

@@ -22,6 +22,7 @@
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.tasks.TaskInfo;
 import org.elasticsearch.test.ESIntegTestCase;
+import org.elasticsearch.test.MockHttpTransport;
 import org.elasticsearch.test.discovery.TestZenDiscovery;
 import org.elasticsearch.xpack.ccr.action.FollowExistingIndexAction;
 import org.elasticsearch.xpack.ccr.action.ShardChangesAction;
@@ -61,7 +62,7 @@ protected Settings nodeSettings(int nodeOrdinal)  {
 
     @Override
     protected Collection<Class<? extends Plugin>> getMockPlugins() {
-        return Arrays.asList(TestSeedPlugin.class, TestZenDiscovery.TestPlugin.class);
+        return Arrays.asList(TestSeedPlugin.class, TestZenDiscovery.TestPlugin.class, MockHttpTransport.TestPlugin.class);
     }
 
     @Override